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3 PCRE - Perl-compatible regular expressions
4 .sp
5 .B #include <pcre.h>
6 .
7 .
9 .rs
10 .sp
11 .SM
12 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
13 .ti +5n
14 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
15 .ti +5n
16 .B const unsigned char *\fItableptr\fP);
17 .PP
18 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
19 .ti +5n
20 .B int *\fIerrorcodeptr\fP,
21 .ti +5n
22 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
23 .ti +5n
24 .B const unsigned char *\fItableptr\fP);
25 .PP
26 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
27 .ti +5n
28 .B const char **\fIerrptr\fP);
29 .PP
30 .B void pcre_free_study(pcre_extra *\fIextra\fP);
31 .PP
32 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
33 .ti +5n
34 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
35 .ti +5n
36 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
37 .PP
38 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
39 .ti +5n
40 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
41 .ti +5n
42 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
43 .ti +5n
44 .B int *\fIworkspace\fP, int \fIwscount\fP);
45 .
46 .
48 .rs
49 .sp
50 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
51 .ti +5n
52 .B const char *\fIsubject\fP, int *\fIovector\fP,
53 .ti +5n
54 .B int \fIstringcount\fP, const char *\fIstringname\fP,
55 .ti +5n
56 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
57 .PP
58 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
59 .ti +5n
60 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
61 .ti +5n
62 .B int \fIbuffersize\fP);
63 .PP
64 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
65 .ti +5n
66 .B const char *\fIsubject\fP, int *\fIovector\fP,
67 .ti +5n
68 .B int \fIstringcount\fP, const char *\fIstringname\fP,
69 .ti +5n
70 .B const char **\fIstringptr\fP);
71 .PP
72 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
73 .ti +5n
74 .B const char *\fIname\fP);
75 .PP
76 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
77 .ti +5n
78 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
79 .PP
80 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
81 .ti +5n
82 .B int \fIstringcount\fP, int \fIstringnumber\fP,
83 .ti +5n
84 .B const char **\fIstringptr\fP);
85 .PP
86 .B int pcre_get_substring_list(const char *\fIsubject\fP,
87 .ti +5n
88 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
89 .PP
90 .B void pcre_free_substring(const char *\fIstringptr\fP);
91 .PP
92 .B void pcre_free_substring_list(const char **\fIstringptr\fP);
93 .
94 .
96 .rs
97 .sp
98 .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
99 .PP
100 .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
101 .PP
102 .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
103 .ti +5n
104 .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
105 .PP
106 .B const unsigned char *pcre_maketables(void);
107 .PP
108 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
109 .ti +5n
110 .B int \fIwhat\fP, void *\fIwhere\fP);
111 .PP
112 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
113 .PP
114 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
115 .PP
116 .B const char *pcre_version(void);
117 .PP
118 .B int pcre_pattern_to_host_byte_order(pcre *\fIcode\fP,
119 .ti +5n
120 .B pcre_extra *\fIextra\fP, const unsigned char *\fItables\fP);
121 .
122 .
124 .rs
125 .sp
126 .B void *(*pcre_malloc)(size_t);
127 .PP
128 .B void (*pcre_free)(void *);
129 .PP
130 .B void *(*pcre_stack_malloc)(size_t);
131 .PP
132 .B void (*pcre_stack_free)(void *);
133 .PP
134 .B int (*pcre_callout)(pcre_callout_block *);
135 .
136 .
138 .rs
139 .sp
140 From release 8.30, PCRE can be compiled as a library for handling 16-bit
141 character strings as well as, or instead of, the original library that handles
142 8-bit character strings. To avoid too much complication, this document
143 describes the 8-bit versions of the functions, with only occasional references
144 to the 16-bit library.
145 .P
146 The 16-bit functions operate in the same way as their 8-bit counterparts; they
147 just use different data types for their arguments and results, and their names
148 start with \fBpcre16_\fP instead of \fBpcre_\fP. For every option that has UTF8
149 in its name (for example, PCRE_UTF8), there is a corresponding 16-bit name with
150 UTF8 replaced by UTF16. This facility is in fact just cosmetic; the 16-bit
151 option names define the same bit values.
152 .P
153 References to bytes and UTF-8 in this document should be read as references to
154 16-bit data quantities and UTF-16 when using the 16-bit library, unless
155 specified otherwise. More details of the specific differences for the 16-bit
156 library are given in the
157 .\" HREF
158 \fBpcre16\fP
159 .\"
160 page.
161 .
162 .
164 .rs
165 .sp
166 PCRE has its own native API, which is described in this document. There are
167 also some wrapper functions (for the 8-bit library only) that correspond to the
168 POSIX regular expression API, but they do not give access to all the
169 functionality. They are described in the
170 .\" HREF
171 \fBpcreposix\fP
172 .\"
173 documentation. Both of these APIs define a set of C function calls. A C++
174 wrapper (again for the 8-bit library only) is also distributed with PCRE. It is
175 documented in the
176 .\" HREF
177 \fBpcrecpp\fP
178 .\"
179 page.
180 .P
181 The native API C function prototypes are defined in the header file
182 \fBpcre.h\fP, and on Unix-like systems the (8-bit) library itself is called
183 \fBlibpcre\fP. It can normally be accessed by adding \fB-lpcre\fP to the
184 command for linking an application that uses PCRE. The header file defines the
185 macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers
186 for the library. Applications can use these to include support for different
187 releases of PCRE.
188 .P
189 In a Windows environment, if you want to statically link an application program
190 against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
191 including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
192 \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
193 \fB__declspec(dllimport)\fP, with unwanted results.
194 .P
195 The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
196 and \fBpcre_exec()\fP are used for compiling and matching regular expressions
197 in a Perl-compatible manner. A sample program that demonstrates the simplest
198 way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
199 source distribution. A listing of this program is given in the
200 .\" HREF
201 \fBpcredemo\fP
202 .\"
203 documentation, and the
204 .\" HREF
205 \fBpcresample\fP
206 .\"
207 documentation describes how to compile and run it.
208 .P
209 Just-in-time compiler support is an optional feature of PCRE that can be built
210 in appropriate hardware environments. It greatly speeds up the matching
211 performance of many patterns. Simple programs can easily request that it be
212 used if available, by setting an option that is ignored when it is not
213 relevant. More complicated programs might need to make use of the functions
214 \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
215 \fBpcre_assign_jit_stack()\fP in order to control the JIT code's memory usage.
216 These functions are discussed in the
217 .\" HREF
218 \fBpcrejit\fP
219 .\"
220 documentation.
221 .P
222 A second matching function, \fBpcre_dfa_exec()\fP, which is not
223 Perl-compatible, is also provided. This uses a different algorithm for the
224 matching. The alternative algorithm finds all possible matches (at a given
225 point in the subject), and scans the subject just once (unless there are
226 lookbehind assertions). However, this algorithm does not return captured
227 substrings. A description of the two matching algorithms and their advantages
228 and disadvantages is given in the
229 .\" HREF
230 \fBpcrematching\fP
231 .\"
232 documentation.
233 .P
234 In addition to the main compiling and matching functions, there are convenience
235 functions for extracting captured substrings from a subject string that is
236 matched by \fBpcre_exec()\fP. They are:
237 .sp
238 \fBpcre_copy_substring()\fP
239 \fBpcre_copy_named_substring()\fP
240 \fBpcre_get_substring()\fP
241 \fBpcre_get_named_substring()\fP
242 \fBpcre_get_substring_list()\fP
243 \fBpcre_get_stringnumber()\fP
244 \fBpcre_get_stringtable_entries()\fP
245 .sp
246 \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
247 provided, to free the memory used for extracted strings.
248 .P
249 The function \fBpcre_maketables()\fP is used to build a set of character tables
250 in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
251 or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
252 specialist use. Most commonly, no special tables are passed, in which case
253 internal tables that are generated when PCRE is built are used.
254 .P
255 The function \fBpcre_fullinfo()\fP is used to find out information about a
256 compiled pattern. The function \fBpcre_version()\fP returns a pointer to a
257 string containing the version of PCRE and its date of release.
258 .P
259 The function \fBpcre_refcount()\fP maintains a reference count in a data block
260 containing a compiled pattern. This is provided for the benefit of
261 object-oriented applications.
262 .P
263 The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
264 the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
265 respectively. PCRE calls the memory management functions via these variables,
266 so a calling program can replace them if it wishes to intercept the calls. This
267 should be done before calling any PCRE functions.
268 .P
269 The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
270 indirections to memory management functions. These special functions are used
271 only when PCRE is compiled to use the heap for remembering data, instead of
272 recursive function calls, when running the \fBpcre_exec()\fP function. See the
273 .\" HREF
274 \fBpcrebuild\fP
275 .\"
276 documentation for details of how to do this. It is a non-standard way of
277 building PCRE, for use in environments that have limited stacks. Because of the
278 greater use of memory management, it runs more slowly. Separate functions are
279 provided so that special-purpose external code can be used for this case. When
280 used, these functions are always called in a stack-like manner (last obtained,
281 first freed), and always for memory blocks of the same size. There is a
282 discussion about PCRE's stack usage in the
283 .\" HREF
284 \fBpcrestack\fP
285 .\"
286 documentation.
287 .P
288 The global variable \fBpcre_callout\fP initially contains NULL. It can be set
289 by the caller to a "callout" function, which PCRE will then call at specified
290 points during a matching operation. Details are given in the
291 .\" HREF
292 \fBpcrecallout\fP
293 .\"
294 documentation.
295 .
296 .
297 .\" HTML <a name="newlines"></a>
299 .rs
300 .sp
301 PCRE supports five different conventions for indicating line breaks in
302 strings: a single CR (carriage return) character, a single LF (linefeed)
303 character, the two-character sequence CRLF, any of the three preceding, or any
304 Unicode newline sequence. The Unicode newline sequences are the three just
305 mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
306 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
307 (paragraph separator, U+2029).
308 .P
309 Each of the first three conventions is used by at least one operating system as
310 its standard newline sequence. When PCRE is built, a default can be specified.
311 The default default is LF, which is the Unix standard. When PCRE is run, the
312 default can be overridden, either when a pattern is compiled, or when it is
313 matched.
314 .P
315 At compile time, the newline convention can be specified by the \fIoptions\fP
316 argument of \fBpcre_compile()\fP, or it can be specified by special text at the
317 start of the pattern itself; this overrides any other settings. See the
318 .\" HREF
319 \fBpcrepattern\fP
320 .\"
321 page for details of the special character sequences.
322 .P
323 In the PCRE documentation the word "newline" is used to mean "the character or
324 pair of characters that indicate a line break". The choice of newline
325 convention affects the handling of the dot, circumflex, and dollar
326 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
327 recognized line ending sequence, the match position advancement for a
328 non-anchored pattern. There is more detail about this in the
329 .\" HTML <a href="#execoptions">
330 .\" </a>
331 section on \fBpcre_exec()\fP options
332 .\"
333 below.
334 .P
335 The choice of newline convention does not affect the interpretation of
336 the \en or \er escape sequences, nor does it affect what \eR matches, which is
337 controlled in a similar way, but by separate options.
338 .
339 .
341 .rs
342 .sp
343 The PCRE functions can be used in multi-threading applications, with the
344 proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
345 \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
346 callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
347 .P
348 The compiled form of a regular expression is not altered during matching, so
349 the same compiled pattern can safely be used by several threads at once.
350 .P
351 If the just-in-time optimization feature is being used, it needs separate
352 memory stack areas for each thread. See the
353 .\" HREF
354 \fBpcrejit\fP
355 .\"
356 documentation for more details.
357 .
358 .
360 .rs
361 .sp
362 The compiled form of a regular expression can be saved and re-used at a later
363 time, possibly by a different program, and even on a host other than the one on
364 which it was compiled. Details are given in the
365 .\" HREF
366 \fBpcreprecompile\fP
367 .\"
368 documentation, which includes a description of the
369 \fBpcre_pattern_to_host_byte_order()\fP function. However, compiling a regular
370 expression with one version of PCRE for use with a different version is not
371 guaranteed to work and may cause crashes.
372 .
373 .
375 .rs
376 .sp
377 .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
378 .PP
379 The function \fBpcre_config()\fP makes it possible for a PCRE client to
380 discover which optional features have been compiled into the PCRE library. The
381 .\" HREF
382 \fBpcrebuild\fP
383 .\"
384 documentation has more details about these optional features.
385 .P
386 The first argument for \fBpcre_config()\fP is an integer, specifying which
387 information is required; the second argument is a pointer to a variable into
388 which the information is placed. The returned value is zero on success, or the
389 negative error code PCRE_ERROR_BADOPTION if the value in the first argument is
390 not recognized. The following information is available:
391 .sp
393 .sp
394 The output is an integer that is set to one if UTF-8 support is available;
395 otherwise it is set to zero. If this option is given to the 16-bit version of
396 this function, \fBpcre16_config()\fP, the result is PCRE_ERROR_BADOPTION.
397 .sp
399 .sp
400 The output is an integer that is set to one if UTF-16 support is available;
401 otherwise it is set to zero. This value should normally be given to the 16-bit
402 version of this function, \fBpcre16_config()\fP. If it is given to the 8-bit
403 version of this function, the result is PCRE_ERROR_BADOPTION.
404 .sp
406 .sp
407 The output is an integer that is set to one if support for Unicode character
408 properties is available; otherwise it is set to zero.
409 .sp
411 .sp
412 The output is an integer that is set to one if support for just-in-time
413 compiling is available; otherwise it is set to zero.
414 .sp
416 .sp
417 The output is a pointer to a zero-terminated "const char *" string. If JIT
418 support is available, the string contains the name of the architecture for
419 which the JIT compiler is configured, for example "x86 32bit (little endian +
420 unaligned)". If JIT support is not available, the result is NULL.
421 .sp
423 .sp
424 The output is an integer whose value specifies the default character sequence
425 that is recognized as meaning "newline". The four values that are supported
426 are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
427 Though they are derived from ASCII, the same values are returned in EBCDIC
428 environments. The default should normally correspond to the standard sequence
429 for your operating system.
430 .sp
432 .sp
433 The output is an integer whose value indicates what character sequences the \eR
434 escape sequence matches by default. A value of 0 means that \eR matches any
435 Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
436 or CRLF. The default can be overridden when a pattern is compiled or matched.
437 .sp
439 .sp
440 The output is an integer that contains the number of bytes used for internal
441 linkage in compiled regular expressions. For the 8-bit library, the value can
442 be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still
443 a number of bytes. The default value of 2 is sufficient for all but the most
444 massive patterns, since it allows the compiled pattern to be up to 64K in size.
445 Larger values allow larger regular expressions to be compiled, at the expense
446 of slower matching.
447 .sp
449 .sp
450 The output is an integer that contains the threshold above which the POSIX
451 interface uses \fBmalloc()\fP for output vectors. Further details are given in
452 the
453 .\" HREF
454 \fBpcreposix\fP
455 .\"
456 documentation.
457 .sp
459 .sp
460 The output is a long integer that gives the default limit for the number of
461 internal matching function calls in a \fBpcre_exec()\fP execution. Further
462 details are given with \fBpcre_exec()\fP below.
463 .sp
465 .sp
466 The output is a long integer that gives the default limit for the depth of
467 recursion when calling the internal matching function in a \fBpcre_exec()\fP
468 execution. Further details are given with \fBpcre_exec()\fP below.
469 .sp
471 .sp
472 The output is an integer that is set to one if internal recursion when running
473 \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
474 to remember their state. This is the usual way that PCRE is compiled. The
475 output is zero if PCRE was compiled to use blocks of data on the heap instead
476 of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
477 \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
478 avoiding the use of the stack.
479 .
480 .
482 .rs
483 .sp
484 .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
485 .ti +5n
486 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
487 .ti +5n
488 .B const unsigned char *\fItableptr\fP);
489 .sp
490 .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
491 .ti +5n
492 .B int *\fIerrorcodeptr\fP,
493 .ti +5n
494 .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
495 .ti +5n
496 .B const unsigned char *\fItableptr\fP);
497 .P
498 Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
499 called to compile a pattern into an internal form. The only difference between
500 the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
501 \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
502 too much repetition, we refer just to \fBpcre_compile()\fP below, but the
503 information applies equally to \fBpcre_compile2()\fP.
504 .P
505 The pattern is a C string terminated by a binary zero, and is passed in the
506 \fIpattern\fP argument. A pointer to a single block of memory that is obtained
507 via \fBpcre_malloc\fP is returned. This contains the compiled code and related
508 data. The \fBpcre\fP type is defined for the returned block; this is a typedef
509 for a structure whose contents are not externally defined. It is up to the
510 caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
511 .P
512 Although the compiled code of a PCRE regex is relocatable, that is, it does not
513 depend on memory location, the complete \fBpcre\fP data block is not
514 fully relocatable, because it may contain a copy of the \fItableptr\fP
515 argument, which is an address (see below).
516 .P
517 The \fIoptions\fP argument contains various bit settings that affect the
518 compilation. It should be zero if no options are required. The available
519 options are described below. Some of them (in particular, those that are
520 compatible with Perl, but some others as well) can also be set and unset from
521 within the pattern (see the detailed description in the
522 .\" HREF
523 \fBpcrepattern\fP
524 .\"
525 documentation). For those options that can be different in different parts of
526 the pattern, the contents of the \fIoptions\fP argument specifies their
527 settings at the start of compilation and execution. The PCRE_ANCHORED,
529 PCRE_NO_START_OPT options can be set at the time of matching as well as at
530 compile time.
531 .P
532 If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
533 Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
534 NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
535 error message. This is a static string that is part of the library. You must
536 not try to free it. Normally, the offset from the start of the pattern to the
537 byte that was being processed when the error was discovered is placed in the
538 variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
539 immediate error is given). However, for an invalid UTF-8 string, the offset is
540 that of the first byte of the failing character.
541 .P
542 Some errors are not detected until the whole pattern has been scanned; in these
543 cases, the offset passed back is the length of the pattern. Note that the
544 offset is in bytes, not characters, even in UTF-8 mode. It may sometimes point
545 into the middle of a UTF-8 character.
546 .P
547 If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
548 \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
549 returned via this argument in the event of an error. This is in addition to the
550 textual error message. Error codes and messages are listed below.
551 .P
552 If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
553 character tables that are built when PCRE is compiled, using the default C
554 locale. Otherwise, \fItableptr\fP must be an address that is the result of a
555 call to \fBpcre_maketables()\fP. This value is stored with the compiled
556 pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
557 passed to it. For more discussion, see the section on locale support below.
558 .P
559 This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
560 .sp
561 pcre *re;
562 const char *error;
563 int erroffset;
564 re = pcre_compile(
565 "^A.*Z", /* the pattern */
566 0, /* default options */
567 &error, /* for error message */
568 &erroffset, /* for error offset */
569 NULL); /* use default character tables */
570 .sp
571 The following names for option bits are defined in the \fBpcre.h\fP header
572 file:
573 .sp
575 .sp
576 If this bit is set, the pattern is forced to be "anchored", that is, it is
577 constrained to match only at the first matching point in the string that is
578 being searched (the "subject string"). This effect can also be achieved by
579 appropriate constructs in the pattern itself, which is the only way to do it in
580 Perl.
581 .sp
583 .sp
584 If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
585 all with number 255, before each pattern item. For discussion of the callout
586 facility, see the
587 .\" HREF
588 \fBpcrecallout\fP
589 .\"
590 documentation.
591 .sp
594 .sp
595 These options (which are mutually exclusive) control what the \eR escape
596 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
597 match any Unicode newline sequence. The default is specified when PCRE is
598 built. It can be overridden from within the pattern, or by setting an option
599 when a compiled pattern is matched.
600 .sp
602 .sp
603 If this bit is set, letters in the pattern match both upper and lower case
604 letters. It is equivalent to Perl's /i option, and it can be changed within a
605 pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
606 concept of case for characters whose values are less than 128, so caseless
607 matching is always possible. For characters with higher values, the concept of
608 case is supported if PCRE is compiled with Unicode property support, but not
609 otherwise. If you want to use caseless matching for characters 128 and above,
610 you must ensure that PCRE is compiled with Unicode property support as well as
611 with UTF-8 support.
612 .sp
614 .sp
615 If this bit is set, a dollar metacharacter in the pattern matches only at the
616 end of the subject string. Without this option, a dollar also matches
617 immediately before a newline at the end of the string (but not before any other
618 newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
619 There is no equivalent to this option in Perl, and no way to set it within a
620 pattern.
621 .sp
623 .sp
624 If this bit is set, a dot metacharacter in the pattern matches a character of
625 any value, including one that indicates a newline. However, it only ever
626 matches one character, even if newlines are coded as CRLF. Without this option,
627 a dot does not match when the current position is at a newline. This option is
628 equivalent to Perl's /s option, and it can be changed within a pattern by a
629 (?s) option setting. A negative class such as [^a] always matches newline
630 characters, independent of the setting of this option.
631 .sp
633 .sp
634 If this bit is set, names used to identify capturing subpatterns need not be
635 unique. This can be helpful for certain types of pattern when it is known that
636 only one instance of the named subpattern can ever be matched. There are more
637 details of named subpatterns below; see also the
638 .\" HREF
639 \fBpcrepattern\fP
640 .\"
641 documentation.
642 .sp
644 .sp
645 If this bit is set, whitespace data characters in the pattern are totally
646 ignored except when escaped or inside a character class. Whitespace does not
647 include the VT character (code 11). In addition, characters between an
648 unescaped # outside a character class and the next newline, inclusive, are also
649 ignored. This is equivalent to Perl's /x option, and it can be changed within a
650 pattern by a (?x) option setting.
651 .P
652 Which characters are interpreted as newlines is controlled by the options
653 passed to \fBpcre_compile()\fP or by a special sequence at the start of the
654 pattern, as described in the section entitled
655 .\" HTML <a href="pcrepattern.html#newlines">
656 .\" </a>
657 "Newline conventions"
658 .\"
659 in the \fBpcrepattern\fP documentation. Note that the end of this type of
660 comment is a literal newline sequence in the pattern; escape sequences that
661 happen to represent a newline do not count.
662 .P
663 This option makes it possible to include comments inside complicated patterns.
664 Note, however, that this applies only to data characters. Whitespace characters
665 may never appear within special character sequences in a pattern, for example
666 within the sequence (?( that introduces a conditional subpattern.
667 .sp
669 .sp
670 This option was invented in order to turn on additional functionality of PCRE
671 that is incompatible with Perl, but it is currently of very little use. When
672 set, any backslash in a pattern that is followed by a letter that has no
673 special meaning causes an error, thus reserving these combinations for future
674 expansion. By default, as in Perl, a backslash followed by a letter with no
675 special meaning is treated as a literal. (Perl can, however, be persuaded to
676 give an error for this, by running it with the -w option.) There are at present
677 no other features controlled by this option. It can also be set by a (?X)
678 option setting within a pattern.
679 .sp
681 .sp
682 If this option is set, an unanchored pattern is required to match before or at
683 the first newline in the subject string, though the matched text may continue
684 over the newline.
685 .sp
687 .sp
688 If this option is set, PCRE's behaviour is changed in some ways so that it is
689 compatible with JavaScript rather than Perl. The changes are as follows:
690 .P
691 (1) A lone closing square bracket in a pattern causes a compile-time error,
692 because this is illegal in JavaScript (by default it is treated as a data
693 character). Thus, the pattern AB]CD becomes illegal when this option is set.
694 .P
695 (2) At run time, a back reference to an unset subpattern group matches an empty
696 string (by default this causes the current matching alternative to fail). A
697 pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
698 an "a" in the subject), whereas it fails by default, for Perl compatibility.
699 .P
700 (3) \eU matches an upper case "U" character; by default \eU causes a compile
701 time error (Perl uses \eU to upper case subsequent characters).
702 .P
703 (4) \eu matches a lower case "u" character unless it is followed by four
704 hexadecimal digits, in which case the hexadecimal number defines the code point
705 to match. By default, \eu causes a compile time error (Perl uses it to upper
706 case the following character).
707 .P
708 (5) \ex matches a lower case "x" character unless it is followed by two
709 hexadecimal digits, in which case the hexadecimal number defines the code point
710 to match. By default, as in Perl, a hexadecimal number is always expected after
711 \ex, but it may have zero, one, or two digits (so, for example, \exz matches a
712 binary zero character followed by z).
713 .sp
715 .sp
716 By default, PCRE treats the subject string as consisting of a single line of
717 characters (even if it actually contains newlines). The "start of line"
718 metacharacter (^) matches only at the start of the string, while the "end of
719 line" metacharacter ($) matches only at the end of the string, or before a
720 terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
721 Perl.
722 .P
723 When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
724 match immediately following or immediately before internal newlines in the
725 subject string, respectively, as well as at the very start and end. This is
726 equivalent to Perl's /m option, and it can be changed within a pattern by a
727 (?m) option setting. If there are no newlines in a subject string, or no
728 occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
729 .sp
735 .sp
736 These options override the default newline definition that was chosen when PCRE
737 was built. Setting the first or the second specifies that a newline is
738 indicated by a single character (CR or LF, respectively). Setting
739 PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
740 CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
741 preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
742 that any Unicode newline sequence should be recognized. The Unicode newline
743 sequences are the three just mentioned, plus the single characters VT (vertical
744 tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
745 separator, U+2028), and PS (paragraph separator, U+2029). For the 8-bit
746 library, the last two are recognized only in UTF-8 mode.
747 .P
748 The newline setting in the options word uses three bits that are treated
749 as a number, giving eight possibilities. Currently only six are used (default
750 plus the five values above). This means that if you set more than one newline
751 option, the combination may or may not be sensible. For example,
753 other combinations may yield unused numbers and cause an error.
754 .P
755 The only time that a line break in a pattern is specially recognized when
756 compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
757 and so are ignored in this mode. Also, an unescaped # outside a character class
758 indicates a comment that lasts until after the next line break sequence. In
759 other circumstances, line break sequences in patterns are treated as literal
760 data.
761 .P
762 The newline option that is set at compile time becomes the default that is used
763 for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
764 .sp
766 .sp
767 If this option is set, it disables the use of numbered capturing parentheses in
768 the pattern. Any opening parenthesis that is not followed by ? behaves as if it
769 were followed by ?: but named parentheses can still be used for capturing (and
770 they acquire numbers in the usual way). There is no equivalent of this option
771 in Perl.
772 .sp
774 .sp
775 This is an option that acts at matching time; that is, it is really an option
776 for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
777 it is remembered with the compiled pattern and assumed at matching time. For
778 details see the discussion of PCRE_NO_START_OPTIMIZE
779 .\" HTML <a href="#execoptions">
780 .\" </a>
781 below.
782 .\"
783 .sp
785 .sp
786 This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
787 \ew, and some of the POSIX character classes. By default, only ASCII characters
788 are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
789 classify characters. More details are given in the section on
790 .\" HTML <a href="pcre.html#genericchartypes">
791 .\" </a>
792 generic character types
793 .\"
794 in the
795 .\" HREF
796 \fBpcrepattern\fP
797 .\"
798 page. If you set PCRE_UCP, matching one of the items it affects takes much
799 longer. The option is available only if PCRE has been compiled with Unicode
800 property support.
801 .sp
803 .sp
804 This option inverts the "greediness" of the quantifiers so that they are not
805 greedy by default, but become greedy if followed by "?". It is not compatible
806 with Perl. It can also be set by a (?U) option setting within the pattern.
807 .sp
809 .sp
810 This option causes PCRE to regard both the pattern and the subject as strings
811 of UTF-8 characters instead of single-byte strings. However, it is available
812 only when PCRE is built to include UTF support. If not, the use of this option
813 provokes an error. Details of how this option changes the behaviour of PCRE are
814 given in the
815 .\" HREF
816 \fBpcreunicode\fP
817 .\"
818 page.
819 .sp
821 .sp
822 When PCRE_UTF8 is set, the validity of the pattern as a UTF-8
823 string is automatically checked. There is a discussion about the
824 .\" HTML <a href="pcreunicode.html#utf8strings">
825 .\" </a>
826 validity of UTF-8 strings
827 .\"
828 in the
829 .\" HREF
830 \fBpcreunicode\fP
831 .\"
832 page. If an invalid UTF-8 sequence is found, \fBpcre_compile()\fP returns an
833 error. If you already know that your pattern is valid, and you want to skip
834 this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option.
835 When it is set, the effect of passing an invalid UTF-8 string as a pattern is
836 undefined. It may cause your program to crash. Note that this option can also
837 be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress the
838 validity checking of subject strings.
839 .
840 .
842 .rs
843 .sp
844 The following table lists the error codes than may be returned by
845 \fBpcre_compile2()\fP, along with the error messages that may be returned by
846 both compiling functions. Note that error messages are always 8-bit ASCII
847 strings, even in 16-bit mode. As PCRE has developed, some error codes have
848 fallen out of use. To avoid confusion, they have not been re-used.
849 .sp
850 0 no error
851 1 \e at end of pattern
852 2 \ec at end of pattern
853 3 unrecognized character follows \e
854 4 numbers out of order in {} quantifier
855 5 number too big in {} quantifier
856 6 missing terminating ] for character class
857 7 invalid escape sequence in character class
858 8 range out of order in character class
859 9 nothing to repeat
860 10 [this code is not in use]
861 11 internal error: unexpected repeat
862 12 unrecognized character after (? or (?-
863 13 POSIX named classes are supported only within a class
864 14 missing )
865 15 reference to non-existent subpattern
866 16 erroffset passed as NULL
867 17 unknown option bit(s) set
868 18 missing ) after comment
869 19 [this code is not in use]
870 20 regular expression is too large
871 21 failed to get memory
872 22 unmatched parentheses
873 23 internal error: code overflow
874 24 unrecognized character after (?<
875 25 lookbehind assertion is not fixed length
876 26 malformed number or name after (?(
877 27 conditional group contains more than two branches
878 28 assertion expected after (?(
879 29 (?R or (?[+-]digits must be followed by )
880 30 unknown POSIX class name
881 31 POSIX collating elements are not supported
882 32 this version of PCRE is compiled without UTF support
883 33 [this code is not in use]
884 34 character value in \ex{...} sequence is too large
885 35 invalid condition (?(0)
886 36 \eC not allowed in lookbehind assertion
887 37 PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
888 38 number after (?C is > 255
889 39 closing ) for (?C expected
890 40 recursive call could loop indefinitely
891 41 unrecognized character after (?P
892 42 syntax error in subpattern name (missing terminator)
893 43 two named subpatterns have the same name
894 44 invalid UTF-8 string (specifically UTF-8)
895 45 support for \eP, \ep, and \eX has not been compiled
896 46 malformed \eP or \ep sequence
897 47 unknown property name after \eP or \ep
898 48 subpattern name is too long (maximum 32 characters)
899 49 too many named subpatterns (maximum 10000)
900 50 [this code is not in use]
901 51 octal value is greater than \e377 in 8-bit non-UTF-8 mode
902 52 internal error: overran compiling workspace
903 53 internal error: previously-checked referenced subpattern
904 not found
905 54 DEFINE group contains more than one branch
906 55 repeating a DEFINE group is not allowed
907 56 inconsistent NEWLINE options
908 57 \eg is not followed by a braced, angle-bracketed, or quoted
909 name/number or by a plain number
910 58 a numbered reference must not be zero
911 59 an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
912 60 (*VERB) not recognized
913 61 number is too big
914 62 subpattern name expected
915 63 digit expected after (?+
916 64 ] is an invalid data character in JavaScript compatibility mode
917 65 different names for subpatterns of the same number are
918 not allowed
919 66 (*MARK) must have an argument
920 67 this version of PCRE is not compiled with Unicode property
921 support
922 68 \ec must be followed by an ASCII character
923 69 \ek is not followed by a braced, angle-bracketed, or quoted name
924 70 internal error: unknown opcode in find_fixedlength()
925 71 \eN is not supported in a class
926 72 too many forward references
927 73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
928 74 invalid UTF-16 string (specifically UTF-16)
929 .sp
930 The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
931 be used if the limits were changed when PCRE was built.
932 .
933 .
934 .\" HTML <a name="studyingapattern"></a>
936 .rs
937 .sp
938 .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
939 .ti +5n
940 .B const char **\fIerrptr\fP);
941 .PP
942 If a compiled pattern is going to be used several times, it is worth spending
943 more time analyzing it in order to speed up the time taken for matching. The
944 function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
945 argument. If studying the pattern produces additional information that will
946 help speed up matching, \fBpcre_study()\fP returns a pointer to a
947 \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
948 results of the study.
949 .P
950 The returned value from \fBpcre_study()\fP can be passed directly to
951 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
952 also contains other fields that can be set by the caller before the block is
953 passed; these are described
954 .\" HTML <a href="#extradata">
955 .\" </a>
956 below
957 .\"
958 in the section on matching a pattern.
959 .P
960 If studying the pattern does not produce any useful information,
961 \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
962 wants to pass any of the other fields to \fBpcre_exec()\fP or
963 \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
964 .P
965 The second argument of \fBpcre_study()\fP contains option bits. There is only
966 one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
967 compiler is available, the pattern is further compiled into machine code that
968 executes much faster than the \fBpcre_exec()\fP matching function. If
969 the just-in-time compiler is not available, this option is ignored. All other
970 bits in the \fIoptions\fP argument must be zero.
971 .P
972 JIT compilation is a heavyweight optimization. It can take some time for
973 patterns to be analyzed, and for one-off matches and simple patterns the
974 benefit of faster execution might be offset by a much slower study time.
975 Not all patterns can be optimized by the JIT compiler. For those that cannot be
976 handled, matching automatically falls back to the \fBpcre_exec()\fP
977 interpreter. For more details, see the
978 .\" HREF
979 \fBpcrejit\fP
980 .\"
981 documentation.
982 .P
983 The third argument for \fBpcre_study()\fP is a pointer for an error message. If
984 studying succeeds (even if no data is returned), the variable it points to is
985 set to NULL. Otherwise it is set to point to a textual error message. This is a
986 static string that is part of the library. You must not try to free it. You
987 should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
988 sure that it has run successfully.
989 .P
990 When you are finished with a pattern, you can free the memory used for the
991 study data by calling \fBpcre_free_study()\fP. This function was added to the
992 API for release 8.20. For earlier versions, the memory could be freed with
993 \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
994 where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
995 new function when convenient.
996 .P
997 This is a typical way in which \fBpcre_study\fP() is used (except that in a
998 real application there should be tests for errors):
999 .sp
1000 int rc;
1001 pcre *re;
1002 pcre_extra *sd;
1003 re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1004 sd = pcre_study(
1005 re, /* result of pcre_compile() */
1006 0, /* no options */
1007 &error); /* set to NULL or points to a message */
1008 rc = pcre_exec( /* see below for details of pcre_exec() options */
1009 re, sd, "subject", 7, 0, 0, ovector, 30);
1010 ...
1011 pcre_free_study(sd);
1012 pcre_free(re);
1013 .sp
1014 Studying a pattern does two things: first, a lower bound for the length of
1015 subject string that is needed to match the pattern is computed. This does not
1016 mean that there are any strings of that length that match, but it does
1017 guarantee that no shorter strings match. The value is used by
1018 \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
1019 match strings that are shorter than the lower bound. You can find out the value
1020 in a calling program via the \fBpcre_fullinfo()\fP function.
1021 .P
1022 Studying a pattern is also useful for non-anchored patterns that do not have a
1023 single fixed starting character. A bitmap of possible starting bytes is
1024 created. This speeds up finding a position in the subject at which to start
1025 matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256.)
1026 .P
1027 These two optimizations apply to both \fBpcre_exec()\fP and
1028 \fBpcre_dfa_exec()\fP. However, they are not used by \fBpcre_exec()\fP if
1029 \fBpcre_study()\fP is called with the PCRE_STUDY_JIT_COMPILE option, and
1030 just-in-time compiling is successful. The optimizations can be disabled by
1031 setting the PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
1032 \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
1033 callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
1034 to make use of these facilities in cases where matching fails. See the
1035 discussion of PCRE_NO_START_OPTIMIZE
1036 .\" HTML <a href="#execoptions">
1037 .\" </a>
1038 below.
1039 .\"
1040 .
1041 .
1042 .\" HTML <a name="localesupport"></a>
1044 .rs
1045 .sp
1046 PCRE handles caseless matching, and determines whether characters are letters,
1047 digits, or whatever, by reference to a set of tables, indexed by character
1048 value. When running in UTF-8 mode, this applies only to characters
1049 with codes less than 128. By default, higher-valued codes never match escapes
1050 such as \ew or \ed, but they can be tested with \ep if PCRE is built with
1051 Unicode character property support. Alternatively, the PCRE_UCP option can be
1052 set at compile time; this causes \ew and friends to use Unicode property
1053 support instead of built-in tables. The use of locales with Unicode is
1054 discouraged. If you are handling characters with codes greater than 128, you
1055 should either use UTF-8 and Unicode, or use locales, but not try to mix the
1056 two.
1057 .P
1058 PCRE contains an internal set of tables that are used when the final argument
1059 of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
1060 Normally, the internal tables recognize only ASCII characters. However, when
1061 PCRE is built, it is possible to cause the internal tables to be rebuilt in the
1062 default "C" locale of the local system, which may cause them to be different.
1063 .P
1064 The internal tables can always be overridden by tables supplied by the
1065 application that calls PCRE. These may be created in a different locale from
1066 the default. As more and more applications change to using Unicode, the need
1067 for this locale support is expected to die away.
1068 .P
1069 External tables are built by calling the \fBpcre_maketables()\fP function,
1070 which has no arguments, in the relevant locale. The result can then be passed
1071 to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
1072 example, to build and use tables that are appropriate for the French locale
1073 (where accented characters with values greater than 128 are treated as letters),
1074 the following code could be used:
1075 .sp
1076 setlocale(LC_CTYPE, "fr_FR");
1077 tables = pcre_maketables();
1078 re = pcre_compile(..., tables);
1079 .sp
1080 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
1081 are using Windows, the name for the French locale is "french".
1082 .P
1083 When \fBpcre_maketables()\fP runs, the tables are built in memory that is
1084 obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
1085 that the memory containing the tables remains available for as long as it is
1086 needed.
1087 .P
1088 The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
1089 pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
1090 and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
1091 pattern, compilation, studying and matching all happen in the same locale, but
1092 different patterns can be compiled in different locales.
1093 .P
1094 It is possible to pass a table pointer or NULL (indicating the use of the
1095 internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
1096 this facility could be used to match a pattern in a different locale from the
1097 one in which it was compiled. Passing table pointers at run time is discussed
1098 below in the section on matching a pattern.
1099 .
1100 .
1101 .\" HTML <a name="infoaboutpattern"></a>
1103 .rs
1104 .sp
1105 .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1106 .ti +5n
1107 .B int \fIwhat\fP, void *\fIwhere\fP);
1108 .PP
1109 The \fBpcre_fullinfo()\fP function returns information about a compiled
1110 pattern. It replaces the \fBpcre_info()\fP function, which was removed from the
1111 library at version 8.30, after more than 10 years of obsolescence.
1112 .P
1113 The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
1114 pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
1115 the pattern was not studied. The third argument specifies which piece of
1116 information is required, and the fourth argument is a pointer to a variable
1117 to receive the data. The yield of the function is zero for success, or one of
1118 the following negative numbers:
1119 .sp
1120 PCRE_ERROR_NULL the argument \fIcode\fP was NULL
1121 the argument \fIwhere\fP was NULL
1122 PCRE_ERROR_BADMAGIC the "magic number" was not found
1123 PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
1124 endianness
1125 PCRE_ERROR_BADOPTION the value of \fIwhat\fP was invalid
1126 .sp
1127 The "magic number" is placed at the start of each compiled pattern as an simple
1128 check against passing an arbitrary memory pointer. The endianness error can
1129 occur if a compiled pattern is saved and reloaded on a different host. Here is
1130 a typical call of \fBpcre_fullinfo()\fP, to obtain the length of the compiled
1131 pattern:
1132 .sp
1133 int rc;
1134 size_t length;
1135 rc = pcre_fullinfo(
1136 re, /* result of pcre_compile() */
1137 sd, /* result of pcre_study(), or NULL */
1138 PCRE_INFO_SIZE, /* what is required */
1139 &length); /* where to put the data */
1140 .sp
1141 The possible values for the third argument are defined in \fBpcre.h\fP, and are
1142 as follows:
1143 .sp
1145 .sp
1146 Return the number of the highest back reference in the pattern. The fourth
1147 argument should point to an \fBint\fP variable. Zero is returned if there are
1148 no back references.
1149 .sp
1151 .sp
1152 Return the number of capturing subpatterns in the pattern. The fourth argument
1153 should point to an \fBint\fP variable.
1154 .sp
1156 .sp
1157 Return a pointer to the internal default character tables within PCRE. The
1158 fourth argument should point to an \fBunsigned char *\fP variable. This
1159 information call is provided for internal use by the \fBpcre_study()\fP
1160 function. External callers can cause PCRE to use its internal tables by passing
1161 a NULL table pointer.
1162 .sp
1164 .sp
1165 Return information about the first data unit of any matched string, for a
1166 non-anchored pattern. (The name of this option refers to the 8-bit library,
1167 where data units are bytes.) The fourth argument should point to an \fBint\fP
1168 variable.
1169 .P
1170 If there is a fixed first value, for example, the letter "c" from a pattern
1171 such as (cat|cow|coyote), its value is returned. In the 8-bit library, the
1172 value is always less than 256; in the 16-bit library the value can be up to
1173 0xffff.
1174 .P
1175 If there is no fixed first value, and if either
1176 .sp
1177 (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
1178 starts with "^", or
1179 .sp
1180 (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
1181 (if it were set, the pattern would be anchored),
1182 .sp
1183 -1 is returned, indicating that the pattern matches only at the start of a
1184 subject string or after any newline within the string. Otherwise -2 is
1185 returned. For anchored patterns, -2 is returned.
1186 .sp
1188 .sp
1189 If the pattern was studied, and this resulted in the construction of a 256-bit
1190 table indicating a fixed set of values for the first data unit in any matching
1191 string, a pointer to the table is returned. Otherwise NULL is returned. The
1192 fourth argument should point to an \fBunsigned char *\fP variable.
1193 .sp
1195 .sp
1196 Return 1 if the pattern contains any explicit matches for CR or LF characters,
1197 otherwise 0. The fourth argument should point to an \fBint\fP variable. An
1198 explicit match is either a literal CR or LF character, or \er or \en.
1199 .sp
1201 .sp
1202 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
1203 0. The fourth argument should point to an \fBint\fP variable. (?J) and
1204 (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1205 .sp
1207 .sp
1208 Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
1209 just-in-time compiling was successful. The fourth argument should point to an
1210 \fBint\fP variable. A return value of 0 means that JIT support is not available
1211 in this version of PCRE, or that the pattern was not studied with the
1212 PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
1213 particular pattern. See the
1214 .\" HREF
1215 \fBpcrejit\fP
1216 .\"
1217 documentation for details of what can and cannot be handled.
1218 .sp
1220 .sp
1221 If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1222 return the size of the JIT compiled code, otherwise return zero. The fourth
1223 argument should point to a \fBsize_t\fP variable.
1224 .sp
1226 .sp
1227 Return the value of the rightmost literal data unit that must exist in any
1228 matched string, other than at its start, if such a value has been recorded. The
1229 fourth argument should point to an \fBint\fP variable. If there is no such
1230 value, -1 is returned. For anchored patterns, a last literal value is recorded
1231 only if it follows something of variable length. For example, for the pattern
1232 /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
1233 is -1.
1234 .sp
1236 .sp
1237 If the pattern was studied and a minimum length for matching subject strings
1238 was computed, its value is returned. Otherwise the returned value is -1. The
1239 value is a number of characters, which in UTF-8 mode may be different from the
1240 number of bytes. The fourth argument should point to an \fBint\fP variable. A
1241 non-negative value is a lower bound to the length of any matching string. There
1242 may not be any strings of that length that do actually match, but every string
1243 that does match is at least that long.
1244 .sp
1248 .sp
1249 PCRE supports the use of named as well as numbered capturing parentheses. The
1250 names are just an additional way of identifying the parentheses, which still
1251 acquire numbers. Several convenience functions such as
1252 \fBpcre_get_named_substring()\fP are provided for extracting captured
1253 substrings by name. It is also possible to extract the data directly, by first
1254 converting the name to a number in order to access the correct pointers in the
1255 output vector (described with \fBpcre_exec()\fP below). To do the conversion,
1256 you need to use the name-to-number map, which is described by these three
1257 values.
1258 .P
1259 The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
1260 the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
1261 entry; both of these return an \fBint\fP value. The entry size depends on the
1262 length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
1263 entry of the table. This is a pointer to \fBchar\fP in the 8-bit library, where
1264 the first two bytes of each entry are the number of the capturing parenthesis,
1265 most significant byte first. In the 16-bit library, the pointer points to
1266 16-bit data units, the first of which contains the parenthesis number. The rest
1267 of the entry is the corresponding name, zero terminated.
1268 .P
1269 The names are in alphabetical order. Duplicate names may appear if (?| is used
1270 to create multiple groups with the same number, as described in the
1271 .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
1272 .\" </a>
1273 section on duplicate subpattern numbers
1274 .\"
1275 in the
1276 .\" HREF
1277 \fBpcrepattern\fP
1278 .\"
1279 page. Duplicate names for subpatterns with different numbers are permitted only
1280 if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
1281 table in the order in which they were found in the pattern. In the absence of
1282 (?| this is the order of increasing number; when (?| is used this is not
1283 necessarily the case because later subpatterns may have lower numbers.
1284 .P
1285 As a simple example of the name/number table, consider the following pattern
1286 after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white
1287 space - including newlines - is ignored):
1288 .sp
1289 .\" JOIN
1290 (?<date> (?<year>(\ed\ed)?\ed\ed) -
1291 (?<month>\ed\ed) - (?<day>\ed\ed) )
1292 .sp
1293 There are four named subpatterns, so the table has four entries, and each entry
1294 in the table is eight bytes long. The table is as follows, with non-printing
1295 bytes shows in hexadecimal, and undefined bytes shown as ??:
1296 .sp
1297 00 01 d a t e 00 ??
1298 00 05 d a y 00 ?? ??
1299 00 04 m o n t h 00
1300 00 02 y e a r 00 ??
1301 .sp
1302 When writing code to extract data from named subpatterns using the
1303 name-to-number map, remember that the length of the entries is likely to be
1304 different for each compiled pattern.
1305 .sp
1307 .sp
1308 Return 1 if the pattern can be used for partial matching with
1309 \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
1310 \fBint\fP variable. From release 8.00, this always returns 1, because the
1311 restrictions that previously applied to partial matching have been lifted. The
1312 .\" HREF
1313 \fBpcrepartial\fP
1314 .\"
1315 documentation gives details of partial matching.
1316 .sp
1318 .sp
1319 Return a copy of the options with which the pattern was compiled. The fourth
1320 argument should point to an \fBunsigned long int\fP variable. These option bits
1321 are those specified in the call to \fBpcre_compile()\fP, modified by any
1322 top-level option settings at the start of the pattern itself. In other words,
1323 they are the options that will be in force when matching starts. For example,
1324 if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
1326 .P
1327 A pattern is automatically anchored by PCRE if all of its top-level
1328 alternatives begin with one of the following:
1329 .sp
1330 ^ unless PCRE_MULTILINE is set
1331 \eA always
1332 \eG always
1333 .\" JOIN
1334 .* if PCRE_DOTALL is set and there are no back
1335 references to the subpattern in which .* appears
1336 .sp
1337 For such patterns, the PCRE_ANCHORED bit is set in the options returned by
1338 \fBpcre_fullinfo()\fP.
1339 .sp
1341 .sp
1342 Return the size of the compiled pattern in bytes (for both libraries). The
1343 fourth argument should point to a \fBsize_t\fP variable. This value does not
1344 include the size of the \fBpcre\fP structure that is returned by
1345 \fBpcre_compile()\fP. The value that is passed as the argument to
1346 \fBpcre_malloc()\fP when \fBpcre_compile()\fP is getting memory in which to
1347 place the compiled data is the value returned by this option plus the size of
1348 the \fBpcre\fP structure. Studying a compiled pattern, with or without JIT,
1349 does not alter the value returned by this option.
1350 .sp
1352 .sp
1353 Return the size in bytes of the data block pointed to by the \fIstudy_data\fP
1354 field in a \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no
1355 study data, zero is returned. The fourth argument should point to a
1356 \fBsize_t\fP variable. The \fIstudy_data\fP field is set by \fBpcre_study()\fP
1357 to record information that will speed up matching (see the section entitled
1358 .\" HTML <a href="#studyingapattern">
1359 .\" </a>
1360 "Studying a pattern"
1361 .\"
1362 above). The format of the \fIstudy_data\fP block is private, but its length
1363 is made available via this option so that it can be saved and restored (see the
1364 .\" HREF
1365 \fBpcreprecompile\fP
1366 .\"
1367 documentation for details).
1368 .
1369 .
1371 .rs
1372 .sp
1373 .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
1374 .PP
1375 The \fBpcre_refcount()\fP function is used to maintain a reference count in the
1376 data block that contains a compiled pattern. It is provided for the benefit of
1377 applications that operate in an object-oriented manner, where different parts
1378 of the application may be using the same compiled pattern, but you want to free
1379 the block when they are all done.
1380 .P
1381 When a pattern is compiled, the reference count field is initialized to zero.
1382 It is changed only by calling this function, whose action is to add the
1383 \fIadjust\fP value (which may be positive or negative) to it. The yield of the
1384 function is the new value. However, the value of the count is constrained to
1385 lie between 0 and 65535, inclusive. If the new value is outside these limits,
1386 it is forced to the appropriate limit value.
1387 .P
1388 Except when it is zero, the reference count is not correctly preserved if a
1389 pattern is compiled on one host and then transferred to a host whose byte-order
1390 is different. (This seems a highly unlikely scenario.)
1391 .
1392 .
1394 .rs
1395 .sp
1396 .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
1397 .ti +5n
1398 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
1399 .ti +5n
1400 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
1401 .P
1402 The function \fBpcre_exec()\fP is called to match a subject string against a
1403 compiled pattern, which is passed in the \fIcode\fP argument. If the
1404 pattern was studied, the result of the study should be passed in the
1405 \fIextra\fP argument. You can call \fBpcre_exec()\fP with the same \fIcode\fP
1406 and \fIextra\fP arguments as many times as you like, in order to match
1407 different subject strings with the same pattern.
1408 .P
1409 This function is the main matching facility of the library, and it operates in
1410 a Perl-like manner. For specialist use there is also an alternative matching
1411 function, which is described
1412 .\" HTML <a href="#dfamatch">
1413 .\" </a>
1414 below
1415 .\"
1416 in the section about the \fBpcre_dfa_exec()\fP function.
1417 .P
1418 In most applications, the pattern will have been compiled (and optionally
1419 studied) in the same process that calls \fBpcre_exec()\fP. However, it is
1420 possible to save compiled patterns and study data, and then use them later
1421 in different processes, possibly even on different hosts. For a discussion
1422 about this, see the
1423 .\" HREF
1424 \fBpcreprecompile\fP
1425 .\"
1426 documentation.
1427 .P
1428 Here is an example of a simple call to \fBpcre_exec()\fP:
1429 .sp
1430 int rc;
1431 int ovector[30];
1432 rc = pcre_exec(
1433 re, /* result of pcre_compile() */
1434 NULL, /* we didn't study the pattern */
1435 "some string", /* the subject string */
1436 11, /* the length of the subject string */
1437 0, /* start at offset 0 in the subject */
1438 0, /* default options */
1439 ovector, /* vector of integers for substring information */
1440 30); /* number of elements (NOT size in bytes) */
1441 .
1442 .
1443 .\" HTML <a name="extradata"></a>
1444 .SS "Extra data for \fBpcre_exec()\fR"
1445 .rs
1446 .sp
1447 If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
1448 data block. The \fBpcre_study()\fP function returns such a block (when it
1449 doesn't return NULL), but you can also create one for yourself, and pass
1450 additional information in it. The \fBpcre_extra\fP block contains the following
1451 fields (not necessarily in this order):
1452 .sp
1453 unsigned long int \fIflags\fP;
1454 void *\fIstudy_data\fP;
1455 void *\fIexecutable_jit\fP;
1456 unsigned long int \fImatch_limit\fP;
1457 unsigned long int \fImatch_limit_recursion\fP;
1458 void *\fIcallout_data\fP;
1459 const unsigned char *\fItables\fP;
1460 unsigned char **\fImark\fP;
1461 .sp
1462 In the 16-bit version of this structure, the \fImark\fP field has type
1463 "PCRE_UCHAR16 **".
1464 .P
1465 The \fIflags\fP field is a bitmap that specifies which of the other fields
1466 are set. The flag bits are:
1467 .sp
1475 .sp
1476 Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
1477 the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
1478 returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
1479 should not set these yourself, but you may add to the block by setting the
1480 other fields and their corresponding flag bits.
1481 .P
1482 The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
1483 vast amount of resources when running patterns that are not going to match,
1484 but which have a very large number of possibilities in their search trees. The
1485 classic example is a pattern that uses nested unlimited repeats.
1486 .P
1487 Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
1488 calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
1489 imposed on the number of times this function is called during a match, which
1490 has the effect of limiting the amount of backtracking that can take place. For
1491 patterns that are not anchored, the count restarts from zero for each position
1492 in the subject string.
1493 .P
1494 When \fBpcre_exec()\fP is called with a pattern that was successfully studied
1495 with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
1496 is entirely different. However, there is still the possibility of runaway
1497 matching that goes on for a very long time, and so the \fImatch_limit\fP value
1498 is also used in this case (but in a different way) to limit how long the
1499 matching can continue.
1500 .P
1501 The default value for the limit can be set when PCRE is built; the default
1502 default is 10 million, which handles all but the most extreme cases. You can
1503 override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
1504 block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
1505 the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
1507 .P
1508 The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
1509 instead of limiting the total number of times that \fBmatch()\fP is called, it
1510 limits the depth of recursion. The recursion depth is a smaller number than the
1511 total number of calls, because not all calls to \fBmatch()\fP are recursive.
1512 This limit is of use only if it is set smaller than \fImatch_limit\fP.
1513 .P
1514 Limiting the recursion depth limits the amount of machine stack that can be
1515 used, or, when PCRE has been compiled to use memory on the heap instead of the
1516 stack, the amount of heap memory that can be used. This limit is not relevant,
1517 and is ignored, if the pattern was successfully studied with
1519 .P
1520 The default value for \fImatch_limit_recursion\fP can be set when PCRE is
1521 built; the default default is the same value as the default for
1522 \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
1523 with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
1524 PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
1525 is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
1526 .P
1527 The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
1528 and is described in the
1529 .\" HREF
1530 \fBpcrecallout\fP
1531 .\"
1532 documentation.
1533 .P
1534 The \fItables\fP field is used to pass a character tables pointer to
1535 \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
1536 pattern. A non-NULL value is stored with the compiled pattern only if custom
1537 tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
1538 If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
1539 internal tables to be used. This facility is helpful when re-using patterns
1540 that have been saved after compiling with an external set of tables, because
1541 the external tables might be at a different address when \fBpcre_exec()\fP is
1542 called. See the
1543 .\" HREF
1544 \fBpcreprecompile\fP
1545 .\"
1546 documentation for a discussion of saving compiled patterns for later use.
1547 .P
1548 If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
1549 be set to point to a suitable variable. If the pattern contains any
1550 backtracking control verbs such as (*MARK:NAME), and the execution ends up with
1551 a name to pass back, a pointer to the name string (zero terminated) is placed
1552 in the variable pointed to by the \fImark\fP field. The names are within the
1553 compiled pattern; if you wish to retain such a name you must copy it before
1554 freeing the memory of a compiled pattern. If there is no name to pass back, the
1555 variable pointed to by the \fImark\fP field is set to NULL. For details of the
1556 backtracking control verbs, see the section entitled
1557 .\" HTML <a href="pcrepattern#backtrackcontrol">
1558 .\" </a>
1559 "Backtracking control"
1560 .\"
1561 in the
1562 .\" HREF
1563 \fBpcrepattern\fP
1564 .\"
1565 documentation.
1566 .
1567 .
1568 .\" HTML <a name="execoptions"></a>
1569 .SS "Option bits for \fBpcre_exec()\fP"
1570 .rs
1571 .sp
1572 The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
1573 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
1577 .P
1578 If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE option,
1579 the only supported options for JIT execution are PCRE_NO_UTF8_CHECK,
1581 particular that partial matching is not supported. If an unsupported option is
1582 used, JIT execution is disabled and the normal interpretive code in
1583 \fBpcre_exec()\fP is run.
1584 .sp
1586 .sp
1587 The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
1588 matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
1589 to be anchored by virtue of its contents, it cannot be made unachored at
1590 matching time.
1591 .sp
1594 .sp
1595 These options (which are mutually exclusive) control what the \eR escape
1596 sequence matches. The choice is either to match only CR, LF, or CRLF, or to
1597 match any Unicode newline sequence. These options override the choice that was
1598 made or defaulted when the pattern was compiled.
1599 .sp
1605 .sp
1606 These options override the newline definition that was chosen or defaulted when
1607 the pattern was compiled. For details, see the description of
1608 \fBpcre_compile()\fP above. During matching, the newline choice affects the
1609 behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
1610 the way the match position is advanced after a match failure for an unanchored
1611 pattern.
1612 .P
1614 match attempt for an unanchored pattern fails when the current position is at a
1615 CRLF sequence, and the pattern contains no explicit matches for CR or LF
1616 characters, the match position is advanced by two characters instead of one, in
1617 other words, to after the CRLF.
1618 .P
1619 The above rule is a compromise that makes the most common cases work as
1620 expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
1621 set), it does not match the string "\er\enA" because, after failing at the
1622 start, it skips both the CR and the LF before retrying. However, the pattern
1623 [\er\en]A does match that string, because it contains an explicit CR or LF
1624 reference, and so advances only by one character after the first failure.
1625 .P
1626 An explicit match for CR of LF is either a literal appearance of one of those
1627 characters, or one of the \er or \en escape sequences. Implicit matches such as
1628 [^X] do not count, nor does \es (which includes CR and LF in the characters
1629 that it matches).
1630 .P
1631 Notwithstanding the above, anomalous effects may still occur when CRLF is a
1632 valid newline sequence and explicit \er or \en escapes appear in the pattern.
1633 .sp
1635 .sp
1636 This option specifies that first character of the subject string is not the
1637 beginning of a line, so the circumflex metacharacter should not match before
1638 it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
1639 never to match. This option affects only the behaviour of the circumflex
1640 metacharacter. It does not affect \eA.
1641 .sp
1643 .sp
1644 This option specifies that the end of the subject string is not the end of a
1645 line, so the dollar metacharacter should not match it nor (except in multiline
1646 mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
1647 compile time) causes dollar never to match. This option affects only the
1648 behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
1649 .sp
1651 .sp
1652 An empty string is not considered to be a valid match if this option is set. If
1653 there are alternatives in the pattern, they are tried. If all the alternatives
1654 match the empty string, the entire match fails. For example, if the pattern
1655 .sp
1656 a?b?
1657 .sp
1658 is applied to a string not beginning with "a" or "b", it matches an empty
1659 string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
1660 valid, so PCRE searches further into the string for occurrences of "a" or "b".
1661 .sp
1663 .sp
1664 This is like PCRE_NOTEMPTY, except that an empty string match that is not at
1665 the start of the subject is permitted. If the pattern is anchored, such a match
1666 can occur only if the pattern contains \eK.
1667 .P
1668 Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
1669 does make a special case of a pattern match of the empty string within its
1670 \fBsplit()\fP function, and when using the /g modifier. It is possible to
1671 emulate Perl's behaviour after matching a null string by first trying the match
1672 again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
1673 if that fails, by advancing the starting offset (see below) and trying an
1674 ordinary match again. There is some code that demonstrates how to do this in
1675 the
1676 .\" HREF
1677 \fBpcredemo\fP
1678 .\"
1679 sample program. In the most general case, you have to check to see if the
1680 newline convention recognizes CRLF as a newline, and if so, and the current
1681 character is CR followed by LF, advance the starting offset by two characters
1682 instead of one.
1683 .sp
1685 .sp
1686 There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
1687 a match, in order to speed up the process. For example, if it is known that an
1688 unanchored match must start with a specific character, it searches the subject
1689 for that character, and fails immediately if it cannot find it, without
1690 actually running the main matching function. This means that a special item
1691 such as (*COMMIT) at the start of a pattern is not considered until after a
1692 suitable starting point for the match has been found. When callouts or (*MARK)
1693 items are in use, these "start-up" optimizations can cause them to be skipped
1694 if the pattern is never actually used. The start-up optimizations are in effect
1695 a pre-scan of the subject that takes place before the pattern is run.
1696 .P
1697 The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
1698 causing performance to suffer, but ensuring that in cases where the result is
1699 "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
1700 are considered at every possible starting position in the subject string. If
1701 PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
1702 time.
1703 .P
1704 Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
1705 Consider the pattern
1706 .sp
1708 .sp
1709 When this is compiled, PCRE records the fact that a match must start with the
1710 character "A". Suppose the subject string is "DEFABC". The start-up
1711 optimization scans along the subject, finds "A" and runs the first match
1712 attempt from there. The (*COMMIT) item means that the pattern must match the
1713 current starting position, which in this case, it does. However, if the same
1714 match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
1715 subject string does not happen. The first match attempt is run starting from
1716 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
1717 the overall result is "no match". If the pattern is studied, more start-up
1718 optimizations may be used. For example, a minimum length for the subject may be
1719 recorded. Consider the pattern
1720 .sp
1721 (*MARK:A)(X|Y)
1722 .sp
1723 The minimum length for a match is one character. If the subject is "ABC", there
1724 will be attempts to match "ABC", "BC", "C", and then finally an empty string.
1725 If the pattern is studied, the final attempt does not take place, because PCRE
1726 knows that the subject is too short, and so the (*MARK) is never encountered.
1727 In this case, studying the pattern does not affect the overall match result,
1728 which is still "no match", but it does affect the auxiliary information that is
1729 returned.
1730 .sp
1732 .sp
1733 When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
1734 string is automatically checked when \fBpcre_exec()\fP is subsequently called.
1735 The value of \fIstartoffset\fP is also checked to ensure that it points to the
1736 start of a UTF-8 character. There is a discussion about the validity of UTF-8
1737 strings in the
1738 .\" HREF
1739 \fBpcreunicode\fP
1740 .\"
1741 page. If an invalid sequence of bytes is found, \fBpcre_exec()\fP returns the
1742 error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
1743 truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both
1744 cases, information about the precise nature of the error may also be returned
1745 (see the descriptions of these errors in the section entitled \fIError return
1746 values from\fP \fBpcre_exec()\fP
1747 .\" HTML <a href="#errorlist">
1748 .\" </a>
1749 below).
1750 .\"
1751 If \fIstartoffset\fP contains a value that does not point to the start of a
1752 UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
1753 returned.
1754 .P
1755 If you already know that your subject is valid, and you want to skip these
1756 checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
1757 calling \fBpcre_exec()\fP. You might want to do this for the second and
1758 subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
1759 all the matches in a single subject string. However, you should be sure that
1760 the value of \fIstartoffset\fP points to the start of a character (or the end
1761 of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
1762 invalid string as a subject or an invalid value of \fIstartoffset\fP is
1763 undefined. Your program may crash.
1764 .sp
1767 .sp
1768 These options turn on the partial matching feature. For backwards
1769 compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
1770 occurs if the end of the subject string is reached successfully, but there are
1771 not enough subject characters to complete the match. If this happens when
1772 PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
1773 testing any remaining alternatives. Only if no complete match can be found is
1774 PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
1775 PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
1776 but only if no complete match can be found.
1777 .P
1778 If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
1779 partial match is found, \fBpcre_exec()\fP immediately returns
1780 PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
1781 when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
1782 important that an alternative complete match.
1783 .P
1784 In both cases, the portion of the string that was inspected when the partial
1785 match was found is set as the first matching string. There is a more detailed
1786 discussion of partial and multi-segment matching, with examples, in the
1787 .\" HREF
1788 \fBpcrepartial\fP
1789 .\"
1790 documentation.
1791 .
1792 .
1793 .SS "The string to be matched by \fBpcre_exec()\fP"
1794 .rs
1795 .sp
1796 The subject string is passed to \fBpcre_exec()\fP as a pointer in
1797 \fIsubject\fP, a length in bytes in \fIlength\fP, and a starting byte offset
1798 in \fIstartoffset\fP. If this is negative or greater than the length of the
1799 subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
1800 offset is zero, the search for a match starts at the beginning of the subject,
1801 and this is by far the most common case. In UTF-8 mode, the byte offset must
1802 point to the start of a UTF-8 character (or the end of the subject). Unlike the
1803 pattern string, the subject may contain binary zero bytes.
1804 .P
1805 A non-zero starting offset is useful when searching for another match in the
1806 same subject by calling \fBpcre_exec()\fP again after a previous success.
1807 Setting \fIstartoffset\fP differs from just passing over a shortened string and
1808 setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
1809 lookbehind. For example, consider the pattern
1810 .sp
1811 \eBiss\eB
1812 .sp
1813 which finds occurrences of "iss" in the middle of words. (\eB matches only if
1814 the current position in the subject is not a word boundary.) When applied to
1815 the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
1816 occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
1817 subject, namely "issipi", it does not match, because \eB is always false at the
1818 start of the subject, which is deemed to be a word boundary. However, if
1819 \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
1820 set to 4, it finds the second occurrence of "iss" because it is able to look
1821 behind the starting point to discover that it is preceded by a letter.
1822 .P
1823 Finding all the matches in a subject is tricky when the pattern can match an
1824 empty string. It is possible to emulate Perl's /g behaviour by first trying the
1825 match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
1826 PCRE_ANCHORED options, and then if that fails, advancing the starting offset
1827 and trying an ordinary match again. There is some code that demonstrates how to
1828 do this in the
1829 .\" HREF
1830 \fBpcredemo\fP
1831 .\"
1832 sample program. In the most general case, you have to check to see if the
1833 newline convention recognizes CRLF as a newline, and if so, and the current
1834 character is CR followed by LF, advance the starting offset by two characters
1835 instead of one.
1836 .P
1837 If a non-zero starting offset is passed when the pattern is anchored, one
1838 attempt to match at the given offset is made. This can only succeed if the
1839 pattern does not require the match to be at the start of the subject.
1840 .
1841 .
1842 .SS "How \fBpcre_exec()\fP returns captured substrings"
1843 .rs
1844 .sp
1845 In general, a pattern matches a certain portion of the subject, and in
1846 addition, further substrings from the subject may be picked out by parts of the
1847 pattern. Following the usage in Jeffrey Friedl's book, this is called
1848 "capturing" in what follows, and the phrase "capturing subpattern" is used for
1849 a fragment of a pattern that picks out a substring. PCRE supports several other
1850 kinds of parenthesized subpattern that do not cause substrings to be captured.
1851 .P
1852 Captured substrings are returned to the caller via a vector of integers whose
1853 address is passed in \fIovector\fP. The number of elements in the vector is
1854 passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
1855 argument is NOT the size of \fIovector\fP in bytes.
1856 .P
1857 The first two-thirds of the vector is used to pass back captured substrings,
1858 each substring using a pair of integers. The remaining third of the vector is
1859 used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
1860 and is not available for passing back information. The number passed in
1861 \fIovecsize\fP should always be a multiple of three. If it is not, it is
1862 rounded down.
1863 .P
1864 When a match is successful, information about captured substrings is returned
1865 in pairs of integers, starting at the beginning of \fIovector\fP, and
1866 continuing up to two-thirds of its length at the most. The first element of
1867 each pair is set to the byte offset of the first character in a substring, and
1868 the second is set to the byte offset of the first character after the end of a
1869 substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
1870 mode. They are not character counts.
1871 .P
1872 The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
1873 portion of the subject string matched by the entire pattern. The next pair is
1874 used for the first capturing subpattern, and so on. The value returned by
1875 \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
1876 For example, if two substrings have been captured, the returned value is 3. If
1877 there are no capturing subpatterns, the return value from a successful match is
1878 1, indicating that just the first pair of offsets has been set.
1879 .P
1880 If a capturing subpattern is matched repeatedly, it is the last portion of the
1881 string that it matched that is returned.
1882 .P
1883 If the vector is too small to hold all the captured substring offsets, it is
1884 used as far as possible (up to two-thirds of its length), and the function
1885 returns a value of zero. If neither the actual string matched not any captured
1886 substrings are of interest, \fBpcre_exec()\fP may be called with \fIovector\fP
1887 passed as NULL and \fIovecsize\fP as zero. However, if the pattern contains
1888 back references and the \fIovector\fP is not big enough to remember the related
1889 substrings, PCRE has to get additional memory for use during matching. Thus it
1890 is usually advisable to supply an \fIovector\fP of reasonable size.
1891 .P
1892 There are some cases where zero is returned (indicating vector overflow) when
1893 in fact the vector is exactly the right size for the final match. For example,
1894 consider the pattern
1895 .sp
1896 (a)(?:(b)c|bd)
1897 .sp
1898 If a vector of 6 elements (allowing for only 1 captured substring) is given
1899 with subject string "abd", \fBpcre_exec()\fP will try to set the second
1900 captured string, thereby recording a vector overflow, before failing to match
1901 "c" and backing up to try the second alternative. The zero return, however,
1902 does correctly indicate that the maximum number of slots (namely 2) have been
1903 filled. In similar cases where there is temporary overflow, but the final
1904 number of used slots is actually less than the maximum, a non-zero value is
1905 returned.
1906 .P
1907 The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
1908 subpatterns there are in a compiled pattern. The smallest size for
1909 \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
1910 the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
1911 .P
1912 It is possible for capturing subpattern number \fIn+1\fP to match some part of
1913 the subject when subpattern \fIn\fP has not been used at all. For example, if
1914 the string "abc" is matched against the pattern (a|(z))(bc) the return from the
1915 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
1916 happens, both values in the offset pairs corresponding to unused subpatterns
1917 are set to -1.
1918 .P
1919 Offset values that correspond to unused subpatterns at the end of the
1920 expression are also set to -1. For example, if the string "abc" is matched
1921 against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
1922 return from the function is 2, because the highest used capturing subpattern
1923 number is 1, and the offsets for for the second and third capturing subpatterns
1924 (assuming the vector is large enough, of course) are set to -1.
1925 .P
1926 \fBNote\fP: Elements in the first two-thirds of \fIovector\fP that do not
1927 correspond to capturing parentheses in the pattern are never changed. That is,
1928 if a pattern contains \fIn\fP capturing parentheses, no more than
1929 \fIovector[0]\fP to \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other
1930 elements (in the first two-thirds) retain whatever values they previously had.
1931 .P
1932 Some convenience functions are provided for extracting the captured substrings
1933 as separate strings. These are described below.
1934 .
1935 .
1936 .\" HTML <a name="errorlist"></a>
1937 .SS "Error return values from \fBpcre_exec()\fP"
1938 .rs
1939 .sp
1940 If \fBpcre_exec()\fP fails, it returns a negative number. The following are
1941 defined in the header file:
1942 .sp
1944 .sp
1945 The subject string did not match the pattern.
1946 .sp
1948 .sp
1949 Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
1950 NULL and \fIovecsize\fP was not zero.
1951 .sp
1953 .sp
1954 An unrecognized bit was set in the \fIoptions\fP argument.
1955 .sp
1957 .sp
1958 PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
1959 the case when it is passed a junk pointer and to detect when a pattern that was
1960 compiled in an environment of one endianness is run in an environment with the
1961 other endianness. This is the error that PCRE gives when the magic number is
1962 not present.
1963 .sp
1965 .sp
1966 While running the pattern match, an unknown item was encountered in the
1967 compiled pattern. This error could be caused by a bug in PCRE or by overwriting
1968 of the compiled pattern.
1969 .sp
1971 .sp
1972 If a pattern contains back references, but the \fIovector\fP that is passed to
1973 \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
1974 gets a block of memory at the start of matching to use for this purpose. If the
1975 call via \fBpcre_malloc()\fP fails, this error is given. The memory is
1976 automatically freed at the end of matching.
1977 .P
1978 This error is also given if \fBpcre_stack_malloc()\fP fails in
1979 \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
1980 \fB--disable-stack-for-recursion\fP.
1981 .sp
1983 .sp
1984 This error is used by the \fBpcre_copy_substring()\fP,
1985 \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
1986 below). It is never returned by \fBpcre_exec()\fP.
1987 .sp
1989 .sp
1990 The backtracking limit, as specified by the \fImatch_limit\fP field in a
1991 \fBpcre_extra\fP structure (or defaulted) was reached. See the description
1992 above.
1993 .sp
1995 .sp
1996 This error is never generated by \fBpcre_exec()\fP itself. It is provided for
1997 use by callout functions that want to yield a distinctive error code. See the
1998 .\" HREF
1999 \fBpcrecallout\fP
2000 .\"
2001 documentation for details.
2002 .sp
2004 .sp
2005 A string that contains an invalid UTF-8 byte sequence was passed as a subject,
2006 and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
2007 (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
2008 UTF-8 character is placed in the first element, and a reason code is placed in
2009 the second element. The reason codes are listed in the
2010 .\" HTML <a href="#badutf8reasons">
2011 .\" </a>
2012 following section.
2013 .\"
2014 For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
2015 truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
2016 PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2017 .sp
2019 .sp
2020 The UTF-8 byte sequence that was passed as a subject was checked and found to
2021 be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
2022 \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
2023 end of the subject.
2024 .sp
2026 .sp
2027 The subject string did not match, but it did match partially. See the
2028 .\" HREF
2029 \fBpcrepartial\fP
2030 .\"
2031 documentation for details of partial matching.
2032 .sp
2034 .sp
2035 This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
2036 option was used with a compiled pattern containing items that were not
2037 supported for partial matching. From release 8.00 onwards, there are no
2038 restrictions on partial matching.
2039 .sp
2041 .sp
2042 An unexpected internal error has occurred. This error could be caused by a bug
2043 in PCRE or by overwriting of the compiled pattern.
2044 .sp
2046 .sp
2047 This error is given if the value of the \fIovecsize\fP argument is negative.
2048 .sp
2050 .sp
2051 The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
2052 field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
2053 description above.
2054 .sp
2056 .sp
2057 An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
2058 .sp
2060 .sp
2061 The value of \fIstartoffset\fP was negative or greater than the length of the
2062 subject, that is, the value in \fIlength\fP.
2063 .sp
2065 .sp
2066 This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
2067 ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
2068 Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
2069 fact sufficient to detect this case, but this special error code for
2070 PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
2071 retained for backwards compatibility.
2072 .sp
2074 .sp
2075 This error is returned when \fBpcre_exec()\fP detects a recursion loop within
2076 the pattern. Specifically, it means that either the whole pattern or a
2077 subpattern has been called recursively for the second time at the same position
2078 in the subject string. Some simple patterns that might do this are detected and
2079 faulted at compile time, but more complicated cases, in particular mutual
2080 recursions between two different subpatterns, cannot be detected until run
2081 time.
2082 .sp
2084 .sp
2085 This error is returned when a pattern that was successfully studied using the
2086 PCRE_STUDY_JIT_COMPILE option is being matched, but the memory available for
2087 the just-in-time processing stack is not large enough. See the
2088 .\" HREF
2089 \fBpcrejit\fP
2090 .\"
2091 documentation for more details.
2092 .sp
2094 .sp
2095 This error is given if a pattern that was compiled by the 8-bit library is
2096 passed to a 16-bit library function, or vice versa.
2097 .sp
2099 .sp
2100 This error is given if a pattern that was compiled and saved is reloaded on a
2101 host with different endianness. The utility function
2102 \fBpcre_pattern_to_host_byte_order()\fP can be used to convert such a pattern
2103 so that it runs on the new host.
2104 .P
2105 Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
2106 .
2107 .
2108 .\" HTML <a name="badutf8reasons"></a>
2109 .SS "Reason codes for invalid UTF-8 strings"
2110 .rs
2111 .sp
2112 This section applies only to the 8-bit library. The corresponding information
2113 for the 16-bit library is given in the
2114 .\" HREF
2115 \fBpcre16\fP
2116 .\"
2117 page.
2118 .P
2119 When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
2120 PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
2121 least 2, the offset of the start of the invalid UTF-8 character is placed in
2122 the first output vector element (\fIovector[0]\fP) and a reason code is placed
2123 in the second element (\fIovector[1]\fP). The reason codes are given names in
2124 the \fBpcre.h\fP header file:
2125 .sp
2131 .sp
2132 The string ends with a truncated UTF-8 character; the code specifies how many
2133 bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
2134 no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
2135 allows for up to 6 bytes, and this is checked first; hence the possibility of
2136 4 or 5 missing bytes.
2137 .sp
2142 PCRE_UTF8_ERR10
2143 .sp
2144 The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
2145 character do not have the binary value 0b10 (that is, either the most
2146 significant bit is 0, or the next bit is 1).
2147 .sp
2148 PCRE_UTF8_ERR11
2149 PCRE_UTF8_ERR12
2150 .sp
2151 A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
2152 these code points are excluded by RFC 3629.
2153 .sp
2154 PCRE_UTF8_ERR13
2155 .sp
2156 A 4-byte character has a value greater than 0x10fff; these code points are
2157 excluded by RFC 3629.
2158 .sp
2159 PCRE_UTF8_ERR14
2160 .sp
2161 A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
2162 code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
2163 from UTF-8.
2164 .sp
2165 PCRE_UTF8_ERR15
2166 PCRE_UTF8_ERR16
2167 PCRE_UTF8_ERR17
2168 PCRE_UTF8_ERR18
2169 PCRE_UTF8_ERR19
2170 .sp
2171 A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
2172 value that can be represented by fewer bytes, which is invalid. For example,
2173 the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
2174 one byte.
2175 .sp
2176 PCRE_UTF8_ERR20
2177 .sp
2178 The two most significant bits of the first byte of a character have the binary
2179 value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
2180 byte can only validly occur as the second or subsequent byte of a multi-byte
2181 character.
2182 .sp
2183 PCRE_UTF8_ERR21
2184 .sp
2185 The first byte of a character has the value 0xfe or 0xff. These values can
2186 never occur in a valid UTF-8 string.
2187 .
2188 .
2190 .rs
2191 .sp
2192 .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2193 .ti +5n
2194 .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
2195 .ti +5n
2196 .B int \fIbuffersize\fP);
2197 .PP
2198 .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
2199 .ti +5n
2200 .B int \fIstringcount\fP, int \fIstringnumber\fP,
2201 .ti +5n
2202 .B const char **\fIstringptr\fP);
2203 .PP
2204 .B int pcre_get_substring_list(const char *\fIsubject\fP,
2205 .ti +5n
2206 .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
2207 .PP
2208 Captured substrings can be accessed directly by using the offsets returned by
2209 \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
2210 \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
2211 \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
2212 as new, separate, zero-terminated strings. These functions identify substrings
2213 by number. The next section describes functions for extracting named
2214 substrings.
2215 .P
2216 A substring that contains a binary zero is correctly extracted and has a
2217 further zero added on the end, but the result is not, of course, a C string.
2218 However, you can process such a string by referring to the length that is
2219 returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
2220 Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
2221 for handling strings containing binary zeros, because the end of the final
2222 string is not independently indicated.
2223 .P
2224 The first three arguments are the same for all three of these functions:
2225 \fIsubject\fP is the subject string that has just been successfully matched,
2226 \fIovector\fP is a pointer to the vector of integer offsets that was passed to
2227 \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
2228 captured by the match, including the substring that matched the entire regular
2229 expression. This is the value returned by \fBpcre_exec()\fP if it is greater
2230 than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
2231 space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
2232 number of elements in the vector divided by three.
2233 .P
2234 The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
2235 extract a single substring, whose number is given as \fIstringnumber\fP. A
2236 value of zero extracts the substring that matched the entire pattern, whereas
2237 higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
2238 the string is placed in \fIbuffer\fP, whose length is given by
2239 \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
2240 obtained via \fBpcre_malloc\fP, and its address is returned via
2241 \fIstringptr\fP. The yield of the function is the length of the string, not
2242 including the terminating zero, or one of these error codes:
2243 .sp
2245 .sp
2246 The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
2247 memory failed for \fBpcre_get_substring()\fP.
2248 .sp
2250 .sp
2251 There is no substring whose number is \fIstringnumber\fP.
2252 .P
2253 The \fBpcre_get_substring_list()\fP function extracts all available substrings
2254 and builds a list of pointers to them. All this is done in a single block of
2255 memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
2256 is returned via \fIlistptr\fP, which is also the start of the list of string
2257 pointers. The end of the list is marked by a NULL pointer. The yield of the
2258 function is zero if all went well, or the error code
2259 .sp
2261 .sp
2262 if the attempt to get the memory block failed.
2263 .P
2264 When any of these functions encounter a substring that is unset, which can
2265 happen when capturing subpattern number \fIn+1\fP matches some part of the
2266 subject, but subpattern \fIn\fP has not been used at all, they return an empty
2267 string. This can be distinguished from a genuine zero-length substring by
2268 inspecting the appropriate offset in \fIovector\fP, which is negative for unset
2269 substrings.
2270 .P
2271 The two convenience functions \fBpcre_free_substring()\fP and
2272 \fBpcre_free_substring_list()\fP can be used to free the memory returned by
2273 a previous call of \fBpcre_get_substring()\fP or
2274 \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
2275 the function pointed to by \fBpcre_free\fP, which of course could be called
2276 directly from a C program. However, PCRE is used in some situations where it is
2277 linked via a special interface to another programming language that cannot use
2278 \fBpcre_free\fP directly; it is for these cases that the functions are
2279 provided.
2280 .
2281 .
2283 .rs
2284 .sp
2285 .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
2286 .ti +5n
2287 .B const char *\fIname\fP);
2288 .PP
2289 .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
2290 .ti +5n
2291 .B const char *\fIsubject\fP, int *\fIovector\fP,
2292 .ti +5n
2293 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2294 .ti +5n
2295 .B char *\fIbuffer\fP, int \fIbuffersize\fP);
2296 .PP
2297 .B int pcre_get_named_substring(const pcre *\fIcode\fP,
2298 .ti +5n
2299 .B const char *\fIsubject\fP, int *\fIovector\fP,
2300 .ti +5n
2301 .B int \fIstringcount\fP, const char *\fIstringname\fP,
2302 .ti +5n
2303 .B const char **\fIstringptr\fP);
2304 .PP
2305 To extract a substring by name, you first have to find associated number.
2306 For example, for this pattern
2307 .sp
2308 (a+)b(?<xxx>\ed+)...
2309 .sp
2310 the number of the subpattern called "xxx" is 2. If the name is known to be
2311 unique (PCRE_DUPNAMES was not set), you can find the number from the name by
2312 calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
2313 pattern, and the second is the name. The yield of the function is the
2314 subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
2315 that name.
2316 .P
2317 Given the number, you can extract the substring directly, or use one of the
2318 functions described in the previous section. For convenience, there are also
2319 two functions that do the whole job.
2320 .P
2321 Most of the arguments of \fBpcre_copy_named_substring()\fP and
2322 \fBpcre_get_named_substring()\fP are the same as those for the similarly named
2323 functions that extract by number. As these are described in the previous
2324 section, they are not re-described here. There are just two differences:
2325 .P
2326 First, instead of a substring number, a substring name is given. Second, there
2327 is an extra argument, given at the start, which is a pointer to the compiled
2328 pattern. This is needed in order to gain access to the name-to-number
2329 translation table.
2330 .P
2331 These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
2332 then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
2333 appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
2334 the behaviour may not be what you want (see the next section).
2335 .P
2336 \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
2337 subpatterns with the same number, as described in the
2338 .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
2339 .\" </a>
2340 section on duplicate subpattern numbers
2341 .\"
2342 in the
2343 .\" HREF
2344 \fBpcrepattern\fP
2345 .\"
2346 page, you cannot use names to distinguish the different subpatterns, because
2347 names are not included in the compiled code. The matching process uses only
2348 numbers. For this reason, the use of different names for subpatterns of the
2349 same number causes an error at compile time.
2350 .
2351 .
2353 .rs
2354 .sp
2355 .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
2356 .ti +5n
2357 .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
2358 .PP
2359 When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
2360 are not required to be unique. (Duplicate names are always allowed for
2361 subpatterns with the same number, created by using the (?| feature. Indeed, if
2362 such subpatterns are named, they are required to use the same names.)
2363 .P
2364 Normally, patterns with duplicate names are such that in any one match, only
2365 one of the named subpatterns participates. An example is shown in the
2366 .\" HREF
2367 \fBpcrepattern\fP
2368 .\"
2369 documentation.
2370 .P
2371 When duplicates are present, \fBpcre_copy_named_substring()\fP and
2372 \fBpcre_get_named_substring()\fP return the first substring corresponding to
2373 the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
2374 returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
2375 returns one of the numbers that are associated with the name, but it is not
2376 defined which it is.
2377 .P
2378 If you want to get full details of all captured substrings for a given name,
2379 you must use the \fBpcre_get_stringtable_entries()\fP function. The first
2380 argument is the compiled pattern, and the second is the name. The third and
2381 fourth are pointers to variables which are updated by the function. After it
2382 has run, they point to the first and last entries in the name-to-number table
2383 for the given name. The function itself returns the length of each entry, or
2384 PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
2385 described above in the section entitled \fIInformation about a pattern\fP
2386 .\" HTML <a href="#infoaboutpattern">
2387 .\" </a>
2388 above.
2389 .\"
2390 Given all the relevant entries for the name, you can extract each of their
2391 numbers, and hence the captured data, if any.
2392 .
2393 .
2395 .rs
2396 .sp
2397 The traditional matching function uses a similar algorithm to Perl, which stops
2398 when it finds the first match, starting at a given point in the subject. If you
2399 want to find all possible matches, or the longest possible match, consider
2400 using the alternative matching function (see below) instead. If you cannot use
2401 the alternative function, but still need to find all possible matches, you
2402 can kludge it up by making use of the callout facility, which is described in
2403 the
2404 .\" HREF
2405 \fBpcrecallout\fP
2406 .\"
2407 documentation.
2408 .P
2409 What you have to do is to insert a callout right at the end of the pattern.
2410 When your callout function is called, extract and save the current matched
2411 substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
2412 other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
2413 will yield PCRE_ERROR_NOMATCH.
2414 .
2415 .
2416 .\" HTML <a name="dfamatch"></a>
2418 .rs
2419 .sp
2420 .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
2421 .ti +5n
2422 .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
2423 .ti +5n
2424 .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
2425 .ti +5n
2426 .B int *\fIworkspace\fP, int \fIwscount\fP);
2427 .P
2428 The function \fBpcre_dfa_exec()\fP is called to match a subject string against
2429 a compiled pattern, using a matching algorithm that scans the subject string
2430 just once, and does not backtrack. This has different characteristics to the
2431 normal algorithm, and is not compatible with Perl. Some of the features of PCRE
2432 patterns are not supported. Nevertheless, there are times when this kind of
2433 matching can be useful. For a discussion of the two matching algorithms, and a
2434 list of features that \fBpcre_dfa_exec()\fP does not support, see the
2435 .\" HREF
2436 \fBpcrematching\fP
2437 .\"
2438 documentation.
2439 .P
2440 The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
2441 \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
2442 different way, and this is described below. The other common arguments are used
2443 in the same way as for \fBpcre_exec()\fP, so their description is not repeated
2444 here.
2445 .P
2446 The two additional arguments provide workspace for the function. The workspace
2447 vector should contain at least 20 elements. It is used for keeping track of
2448 multiple paths through the pattern tree. More workspace will be needed for
2449 patterns and subjects where there are a lot of potential matches.
2450 .P
2451 Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
2452 .sp
2453 int rc;
2454 int ovector[10];
2455 int wspace[20];
2456 rc = pcre_dfa_exec(
2457 re, /* result of pcre_compile() */
2458 NULL, /* we didn't study the pattern */
2459 "some string", /* the subject string */
2460 11, /* the length of the subject string */
2461 0, /* start at offset 0 in the subject */
2462 0, /* default options */
2463 ovector, /* vector of integers for substring information */
2464 10, /* number of elements (NOT size in bytes) */
2465 wspace, /* working space vector */
2466 20); /* number of elements (NOT size in bytes) */
2467 .
2468 .SS "Option bits for \fBpcre_dfa_exec()\fP"
2469 .rs
2470 .sp
2471 The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
2472 zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
2476 All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
2477 so their description is not repeated here.
2478 .sp
2481 .sp
2482 These have the same general effect as they do for \fBpcre_exec()\fP, but the
2483 details are slightly different. When PCRE_PARTIAL_HARD is set for
2484 \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
2485 is reached and there is still at least one matching possibility that requires
2486 additional characters. This happens even if some complete matches have also
2487 been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
2488 is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
2489 there have been no complete matches, but there is still at least one matching
2490 possibility. The portion of the string that was inspected when the longest
2491 partial match was found is set as the first matching string in both cases.
2492 There is a more detailed discussion of partial and multi-segment matching, with
2493 examples, in the
2494 .\" HREF
2495 \fBpcrepartial\fP
2496 .\"
2497 documentation.
2498 .sp
2500 .sp
2501 Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
2502 soon as it has found one match. Because of the way the alternative algorithm
2503 works, this is necessarily the shortest possible match at the first possible
2504 matching point in the subject string.
2505 .sp
2507 .sp
2508 When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
2509 again, with additional subject characters, and have it continue with the same
2510 match. The PCRE_DFA_RESTART option requests this action; when it is set, the
2511 \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
2512 before because data about the match so far is left in them after a partial
2513 match. There is more discussion of this facility in the
2514 .\" HREF
2515 \fBpcrepartial\fP
2516 .\"
2517 documentation.
2518 .
2519 .
2520 .SS "Successful returns from \fBpcre_dfa_exec()\fP"
2521 .rs
2522 .sp
2523 When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
2524 substring in the subject. Note, however, that all the matches from one run of
2525 the function start at the same point in the subject. The shorter matches are
2526 all initial substrings of the longer matches. For example, if the pattern
2527 .sp
2528 <.*>
2529 .sp
2530 is matched against the string
2531 .sp
2532 This is <something> <something else> <something further> no more
2533 .sp
2534 the three matched strings are
2535 .sp
2536 <something>
2537 <something> <something else>
2538 <something> <something else> <something further>
2539 .sp
2540 On success, the yield of the function is a number greater than zero, which is
2541 the number of matched substrings. The substrings themselves are returned in
2542 \fIovector\fP. Each string uses two elements; the first is the offset to the
2543 start, and the second is the offset to the end. In fact, all the strings have
2544 the same start offset. (Space could have been saved by giving this only once,
2545 but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
2546 returns data, even though the meaning of the strings is different.)
2547 .P
2548 The strings are returned in reverse order of length; that is, the longest
2549 matching string is given first. If there were too many matches to fit into
2550 \fIovector\fP, the yield of the function is zero, and the vector is filled with
2551 the longest matches. Unlike \fBpcre_exec()\fP, \fBpcre_dfa_exec()\fP can use
2552 the entire \fIovector\fP for returning matched strings.
2553 .
2554 .
2555 .SS "Error returns from \fBpcre_dfa_exec()\fP"
2556 .rs
2557 .sp
2558 The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
2559 Many of the errors are the same as for \fBpcre_exec()\fP, and these are
2560 described
2561 .\" HTML <a href="#errorlist">
2562 .\" </a>
2563 above.
2564 .\"
2565 There are in addition the following errors that are specific to
2566 \fBpcre_dfa_exec()\fP:
2567 .sp
2569 .sp
2570 This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
2571 that it does not support, for instance, the use of \eC or a back reference.
2572 .sp
2574 .sp
2575 This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
2576 uses a back reference for the condition, or a test for recursion in a specific
2577 group. These are not supported.
2578 .sp
2580 .sp
2581 This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
2582 block that contains a setting of the \fImatch_limit\fP or
2583 \fImatch_limit_recursion\fP fields. This is not supported (these fields are
2584 meaningless for DFA matching).
2585 .sp
2587 .sp
2588 This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
2589 \fIworkspace\fP vector.
2590 .sp
2592 .sp
2593 When a recursive subpattern is processed, the matching function calls itself
2594 recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
2595 error is given if the output vector is not large enough. This should be
2596 extremely rare, as a vector of size 1000 is used.
2597 .
2598 .
2599 .SH "SEE ALSO"
2600 .rs
2601 .sp
2602 \fBpcre16\fP(3), \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
2603 \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
2604 \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
2605 .
2606 .
2608 .rs
2609 .sp
2610 .nf
2611 Philip Hazel
2612 University Computing Service
2613 Cambridge CB2 3QH, England.
2614 .fi
2615 .
2616 .
2618 .rs
2619 .sp
2620 .nf
2621 Last updated: 17 January 2012
2622 Copyright (c) 1997-2012 University of Cambridge.
2623 .fi


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